<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="/js/jquery.min.js"></script>
    <script>
        $(function () {
            // var aaa = $("div").first();
            // alert(aaa.html());

            var aaa = $("div:first");
            aaa.css("color", "red");

            var bbb = $("div:last");
            bbb.css("color", "blue");

            var ccc = $("div:even");
            ccc.css("color", "green");

            var ddd = $("div:odd");
            ddd.css("color", "yellow");

        })
    </script>
</head>
<body>
    <div>哈哈哈</div>
    <div>嘻嘻嘻</div>
    <div>哼哼哼</div>
    <div>呵呵呵</div>
    <div>嘿嘿嘿</div>
</body>
</html>